Abstract: Laboratory triaxial tests are carried out in order to understand the strength property of undisturbed and remolded grassroots-reinforced soil (UGRS and RGRS). The influence of root content on soil strength is investigated. Moreover, the strength difference between the two soils is quantitatively described by root content. The laboratory test results show that: (1) As to UGRS, the increase of root content has little effect on the internal friction angle, while it can improve the cohesion which increases first and then keeps unchanged; (2) There is an optimal root content in RGRS making soil strength the highest, which increases with the increasing confining pressure; (3) When the root content in RGRS is 4~6 times that in UGRS, the deviator stresses of RGRS and UGRS in the limit equilibrium state are almost equal.